A magnetic write head for heat assisted magnetic recording having a novel heat sink structure. The write head includes a magnetic write pole and a thermal transducer located adjacent to a leading edge of the magnetic write pole. A heat sink structure, constructed of a non-magnetic, thermally conductive material such as Au, Ag or Cu partially surrounds the magnetic write pole. The heat sink structure can be formed to contact first and second sides of the magnetic write pole, and can be recessed from the media facing surface of the write head. The space between the heat sink structure and the media facing surface can be filled with a physically hard, non-corrosive metal.
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27. A magnetic recording head comprising:
a magnetic write pole that extends to a media facing surface;
a non-magnetic heat sink structure partially surrounding the magnetic write pole and having a leading edge surface;
a thermal transducer located adjacent to a leading edge of the magnetic write pole; and
a wave guide structure separated from the heat sink structure by a non-metallic spacer structure that causes the leading edge surface of the heat sink structure to step away from the wave guide structure, wherein the non-metallic spacer structure is recessed from the media facing surface.
1. A magnetic recording head, comprising:
a magnetic write pole that extends to a media facing surface, the magnetic write pole having first and second laterally opposed sides; and
a heat sink structure comprising a non-magnetic, thermally conductive material, the heat sink structure being formed adjacent to each of the first and second laterally opposed sides of the magnetic write pole, wherein the heat sink structure has a leading edge surface, a portion of which is formed on a non-metallic spacer structure that is recessed from the media facing surface; and
a wave guide structure, and wherein the non-metallic spacer structure is located between the heat sink structure and the wave guide structure and causes the leading edge surface of the heat sink structure to step away from the wave guide structure.
16. A slider for data recording, comprising:
a slider body having a media facing surface, a trailing edge surface and a backside opposite the media facing surface;
a magnetic write head formed on the slider body, the magnetic write head comprising:
a magnetic write pole having first and second laterally opposed sides,
a plasmonic antenna located adjacent to the magnetic write pole, and
a heat sink structure adjacent to each of the first and second laterally opposed sides of the magnetic write pole and extending laterally outward there-from;
a light source formed on the slider body;
a waveguide extending between the light source and the plasmonic antenna; and
a non-metallic spacer located between the heat sink structure and the waveguide, the non-metallic spacer being recessed from the media facing surface.
2. The magnetic recording head as in
3. The magnetic recording head as in
4. The magnetic recording head as in
5. The magnetic recording head as in
6. The magnetic recording head as in
7. The magnetic recording head as in
8. The magnetic recording head as in
9. The magnetic recording head as in
10. The magnetic recording head as in
11. The magnetic recording head as in
the heat sink structure has a centrally disposed portion, an outer portion and an intermediate portion located between the outer portion and the centrally disposed portion;
the centrally disposed portion is recessed from the media facing surface;
the intermediate portion tapers away from the media facing surface at a first angle; and
the outer portion tapers away from the media facing surface at a second angle that is less than the first angle.
12. The magnetic recording head as in
13. The magnetic recording head as in
14. The magnetic recording head as in
15. A magnetic recording head as in
a near field transducer; and
a thin metallic, thermally conductive layer contacting the leading edge surface of the heat sink structure, at least a portion of the thin metallic, thermally conductive layer being located between the heat sink structure and the near field transducer.
17. The slider as in
18. The slider as in
20. The slider as in
21. The slider as in
22. The slider as in
23. The slider as in
24. The slider as in
26. The slider as in
28. The magnetic recording head as in
29. The magnetic recording head as in
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The present application is a Continuation In Part application of commonly assigned U.S. patent application Ser. No. 15/369,730, filed Dec. 5, 2016, entitled, HEAT ASSISTED MAGNETIC DATA RECORDING HEAD WITH HEAT SINK.
The present invention relates to magnetic data recording, and more specifically to a heat assisted magnetic recording head with a heat sink structure adjacent to a magnetic write pole.
Modern day information is commonly stored in magnetic disk drives that include a rotating magnetic disk and a slider containing one or more magnetic head assemblies that house read and write heads that are suspended over the disk by a swinging suspension arm. When the disk rotates, air flows underneath the slider and causes it to lift off and ‘fly’ over the surface of the rotating disk, allowing for the magnetic heads to be employed via processing circuitry to read and write magnetic impressions to and from the rotating disk.
The write head includes at least one coil, a write pole, and one or more return poles. When current flows through the coil, it induces a magnetic field that emanates from the write pole into the disk. The magnetic field is sufficiently strong that it locally magnetizes a portion of the magnetic media, thus allowing for data bits to be recorded onto the disk. After passing through the magnetic layer, the magnetic field travels through the rest of the disk and completes its path by returning to the return pole of the write head.
Once a data bit is recorded onto the disk, its magnetic state can be read with a magnetoresistive sensor, such as giant magnetoresistive (GMR) or a tunnel junction magnetoresistive (TMR) sensor that has a measurable electrical resistance that changes in response to the magnetic field state of the recorded data bit.
This read/write method is the recording technique typically implemented in conventional perpendicular magnetic recording (PMR). However, as data density needs increase and data bits are made smaller and packed closer together, they become thermally unstable and prone to demagnetization. One way to circumvent this problem is to make the recording media more magnetically stiff, i.e., have a higher magnetic anisotropy. However, ‘stiffer’ media also require higher recording magnetic fields, something which is in itself a limitation since in order to record smaller data bits, the write pole size also needs to be reduced, and this in turn reduces the strength of the magnetic field that can be delivered to the disk.
A solution to this challenge is to use heat assisted magnetic recording (HAMR) in which data bits are defined by locally heating the media through the use of a near field thermal transducer (NFT) just at the location on the disk that is to be recorded. The heating process temporarily lowers the magnetic anisotropy of the media, thus ‘softening’ it and allowing it to be recorded with the write pole at write fields that would otherwise be too weak to induce magnetization. Then, after the data has been written, as the disk spins past the NFT, the media cools, causing the anisotropy of the media to rise again, thereby ensuring that the media ‘freezes in’ the magnetic state of the recorded data bit.
One embodiment of the present invention provides a magnetic recording head for heat assisted magnetic recording. The magnetic recording head includes a magnetic write pole that extends to a media facing surface, the magnetic write pole having first and second laterally opposed sides. The magnetic recording head also includes a heat sink structure comprising a non-magnetic, thermally conductive material formed adjacent to each of the first and second laterally opposed sides of the magnetic write pole.
The heat sink structure can be formed of a material such as Au, Ag or Cu, and can be formed to contact each of the first and second sides of the magnetic write pole. The heat sink structure can be formed such that it is recessed from the media facing surface to avoid corrosion and diamond particle embedment and can be formed with a centrally disposed portion that is recessed from the media facing surface and with outer portions that taper further away from the media facing surface as they extend laterally outward from the centrally disposed portion.
The magnetic recording head can also include a thermal transducer with a plasmonic antenna located at the media facing surface and located adjacent to a leading edge of the write pole and a waveguide extending through the recording head. A non-metallic spacer can be included between the waveguide and the heat sink structure to prevent the heat sink structure from interfering with light propagation through the waveguide. The non-metallic spacer can be recessed from the media facing surface by a distance greater than the centrally disposed portion of the heat sink structure.
One embodiment of the present invention provides a method for manufacturing a magnetic write head having a heat sink structure. The method includes forming a magnetic write pole over a substrate, the write pole having first and second sides. A non-magnetic fill material is deposited, and a chemical mechanical polishing process is performed. After performing the chemical mechanical polishing, a non-magnetic heat sink structure is formed so as to extend from the sides of the magnetic write pole.
The process advantageously forms a magnetic write pole and heat sink structure in a magnetic write head that is free of voids at the media facing surface. This advantage can be realized by planarizing the write pole structure by chemical mechanical polishing prior to defining the heat sink structure. This allows the heat sink structure to be formed over a lower topography than would be the case over the as-deposited write pole, thereby minimizing shadowing effects from the write pole structure.
These and other features and advantages of the invention will become apparent upon reading of the following detailed description of the embodiments taken in conjunction with the figures in which consistent reference numbering is used to indicate similar elements throughout.
For a fuller understanding of the nature and advantages of this invention, as well as to illustrate the preferred mode of use, reference should be made to the following detailed description, read in conjunction with the accompanying drawings, which for clarity are not drawn to scale.
The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.
At least one slider 113 is positioned near the magnetic disk 112, with each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, the slider 113 moves in and out over the disk surface 122 so that the head assembly 121 can access different tracks on the disk. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force, which biases the slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127, which may be a voice coil motor (VCM) comprised of a coil that is movable according to a magnetic field. The direction and speed of the coil movement is controlled by the motor current signals supplied by the control unit 129.
During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122, which exerts an upward force, or lift, on the slider. The air bearing thus counter-balances the slight spring force of the suspension 115 and supports the slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation conditions.
The various components of the disk storage system are controlled by access control and internal clock signals that are generated by a control unit 129, typically comprised of logic control circuits and a microprocessor. An aspect of the control unit 129 will be discussed below in greater detail with reference to
The write element 204 includes a magnetic write pole 214, and a magnetic return pole 216, both of which extend to the media facing surface (MFS) of the head. The return pole 216 can be formed with a pedestal 229 at its end near the media facing surface MFS, the pedestal being formed to extend toward the write pole 214. The write pole 214 is connected to a main pole structure 220 that connects to the return pole 216 via a back gap structure 218.
An electrically conductive, non-magnetic write coil 222, shown in cross section in
However, as data density needs increase, the size of the write pole is decreased and data bits are made smaller and packed closer together until they become thermally unstable and prone to demagnetization. One way to circumvent this problem is to construct the magnetic media of a higher anisotropy magnetic material. However, while this makes the magnetic media more stable, it also causes it to require stronger recording magnetic write fields, a problem that is exacerbated by the fact that smaller write poles output a weaker magnetic field, thus making it difficult for recording to occur.
This challenge can be overcome by the use of heat assisted magnetic recording (HAMR) in which highly anisotropic magnetic media is locally heated to temporarily lower its anisotropy, thus allowing for magnetic recording to occur. Then, as the disk moves past the hotspot, the media cools, and its anisotropy again increases, thus ensuring the magnetic stability of the recorded data on the disk.
To this end, the magnetic write element 204 can include a near field transducer (NFT) 226 that extends to the media facing surface (MFS) at a location adjacent to the leading edge of the write pole 214. The near field transducer 226 is optically connected with a light source, such as a laser 228 that can be located at the backside of the slider on which the magnetic head 200 is formed. The light from the laser 228 can be delivered to the near field transducer via the use of an optical waveguide element 230. A thermal shunt 227 may also be provided. The thermal shunt 227, which will be described in greater detail herein below, can be constructed of a thermally conductive material and can be located just above the near field transducer 226, between the near field transducer 226 and the write pole 214.
The near field transducer 226 generates an optical near-field in the vicinity of the apex of the near field transducer antenna 226, and this optical near-field heats the recording disk for recording. At the same time, the temperature of the near field transducer 226 increases due to light absorption by the near field transducer 226. The temperature rise at the near field transducer causes deformation of the near field transducer 226, which degrades recording performance. To reduce the near field transducer temperature, a heat sink structure 302 is provided. The heat sink structure 302 is formed around the main magnetic pole 214. The thermal shunt 227 is formed between the near field transducer 226 and the heat sink structure 302. Heat generated at the near field transducer 226 flows to the heat sink structure 302 through the thermal shunt 227. To facilitate this heat flow, the thermal shunt can be constructed of a thermally conductive material such as Au, Ag or Cu.
In addition to deformation of the near field transducer 226, the heating from the near field transducer 226 can also lead to heating of the write pole 214. This heating can result in crystallographic changes in the write pole and also can result in oxidation of the write pole 214, leading to degraded magnetic performance. This heating of the write pole 214 can be mitigated by the presence of the heat sink structure 302. The heat sink structure 302 can be formed at either side of the write pole 214 and can be formed to contact the sides of the write pole 214.
In one embodiment, the heat sink structure 302 is formed of a non-magnetic material having a high thermal conductivity such as Cu, Ag or Au. In one embodiment, the area beyond the heat sink structure 302 is filled with a non-magnetic fill material 304 such as alumina (Al2O3).
One challenge that can arise from the construction of the heat sink structure 302, is that of voids being formed in the fill layer 304 at the MFS. This formation of voids can lead to corrosion and wear problems and can seriously shorten the life of the write head 204. The inventors have found that these voids are the result of forming the heat shield over a tall, non-planarized write pole structure 214 after defining the write pole. If the fill layer is deposited over these tall write pole and heat shield structures, shadowing from these structures causes problematic void formation in the fill layer 304 at the media facing surface. A process described herein below can, however, advantageously form the desired heat sink structure 302 while completely avoiding problematic void formation in the fill material 304.
With reference to
Then, an ion milling process can be performed to remove material not protected by the mask 602 so as to leave a write pole structure 504 as shown in
With reference now to
With reference now to
With reference to
With reference now to
Then, with reference to
Another chemical mechanical polishing can then be performed, leaving a structure as shown in
The above described process forms a heat sink structure without forming voids at the media facing surface (MFS). Because the write pole is planarized by chemical mechanical polishing before plating of the heat sink structure, the heat sink structure does not have to be formed over the tall topography of the as plated write pole. Also, depositing the final fill layer over the previously planarized heat sink structure further prevents the formation of voids in the fill material at the media facing surface.
The above described process for forming a magnetic write head can be summarized with reference to the flowchart illustrated in
Then, in a step 1804, a first fill layer such as alumina is deposited. Then, in a step 1806 a first chemical mechanical polishing (CMP) is performed. The first CMP is performed sufficiently to reduce the thickness of the write pole to a first or intermediate thickness. Then, in a step 1808 a heat sink is formed. The heat sink can be formed by defining a trench in the first fill layer and electroplating a thermally conductive material such as Cu into the trench. Then, in a step 1810 a second fill layer, such as alumina, is deposited, and in a step 1812 a second chemical mechanical polishing (CMP) is performed. The second CMP is performed to further reduce the thickness of the write pole to a second, thickness that is a final thickness of the write pole.
Novel Heat Sink Structure:
A waveguide core 1906 and cladding material 1908 together form a waveguide 1909. Light from a laser diode (not shown in
The near field transducer 1904 focuses light. A surface Plasmon is generated at the surface of the wing 1910 (which is a surface that faces the waveguide 1909), and it propagates toward the media facing surface (not shown in
Use of the near field transducer 1904 causes heating of the near field transducer 1904 and surrounding structure, including the write pole 1902. In order to reduce this heating of the write pole structure 1902, a heat sink structure 1912 is formed to partially surround the write pole 1902. The heat sink structure 1912 has a novel design that optimizes the transfer of heat from the write pole 1902. As can be seen in
The shape of the heat sink structure 1912 can be more clearly understood with reference to
In order to maximize the thermal efficiency of the heat sink structure 1912 in conducting heat away from the write pole 1902 and antenna 1904 (
In order to prevent this corrosion, smearing and diamond embedment, the heat sink structure 1912 is recessed from the media facing surface MFS. The space between the heat sink structure 1912 and the media facing surface MFS can be filled with a physically hard, non-corrosive material such as alumina (Al2O3) 2002. The fill material 2002 can also be a physically hard, non-corrosive metal, such as: Cr, Rh, Ru, Pd, Pt, Ti, Zr, Hf, Ir, W, Pt or oxides of these materials. The use of such hard metals can further improve heat conduction, such as between the heat sink structure 1912 and the thermal shunt 1914.
As can be seen in
However in order to prevent de-lamination of the hard, non-corrosive material 2002, the heat sink structure 1912 sweeps back away from the media facing surface MFS as it extends laterally outward from the centrally disposed portion 2004. This provides a larger physical amount of fill material 2002 in the outer regions to increase physical robustness of the fill layer 2002 in these regions.
In one possible embodiment, the heat sink structure has an outer portion 2006 and an intermediate portion 2008 that is located between the centrally disposed portion 2004 and outer portion 2006. The intermediate portion 2008 can sweep away from the media facing surface MFS at a first angle 2010, and the outer portion can sweep away from the media facing surface MFS at a second angle 2012. The first angle 2010 is preferably a larger angle than the second angel 2012. For example, the first angle 2010 can be about 45 degrees or 20-70 degrees, whereas the second angle 2012 can be about 10 degrees or 5-30 degrees.
Similarly, the heat sink structure 1912 can have a back edge with, an outer portion 2016 and an intermediate portion 2018. The outer portion 2016 can have a back edge that is substantially parallel with the media facing surface MFS, and the intermediate portion 2018 can have a back edge that tapers away from the media facing surface at an angle 2020 relative to a plane that is parallel with the media facing surface. In one possible embodiment, the angle 2020 can be about 45 degrees or 40-50 degrees.
As can be seen in
For heat transfer purposes, it is desirable for the width W1 of the front edge of the centrally disposed portion 2004 to be as large as possible. However, a larger area with a small recess also promotes de-lamination of the fill layer 2002, which can result in failure of the write head. Therefore, the width W1 of the front edge of the centrally disposed portion 2004 is preferably not too large. In one embodiment, the width W1 of the front edge of the centrally disposed portion 2004 is preferably less than 10 um, and is preferably recessed by a distance R that is 50-400 nm.
In one embodiment, the heat sink structure 1912 can have a total width W2 of greater than 30 um in order to reduce near field transducer temperature. Similarly, the heat sink structure can have a total height H, as measured perpendicular to the media facing surface MFS, of greater than 10 um in order to maintain low near field transducer temperature. Also, in order to maintain low near field transducer temperature, the heat sink structure 1912 can have a thickness measured perpendicular to the page in
As discussed above, it is desirable that the heat sink structure 1912 have a centrally disposed opening 2022 at its back portion opposite the media facing surface MFS in order to avoid interaction between the heat sink structure and an evanescent wave in the wave guide structure (not shown in
During operation of heat assisted recording, an evanescent wave propagates at the interface between the waveguide core 1906 and the cladding 1908. If the distance between the heat sink structure 1912 and the waveguide core 1906 is too small, there will be a loss of light propagation as result of interaction between the heat sink 1912 and the evanescent wave. In order to prevent this, a non-metallic spacer material 2102 can be provided between the heat sink 1912 and the cladding material to form a bump at a location that is recessed from the media facing surface. That is, the spacer material 2102 separates the heat sink structure 1912 from the cladding material 1908. The spacer material 2102 preferably does not extend to the media facing surface MFS, but is recessed from the media facing surface MFS by a distance greater than the recess of the centrally disposed portion 2004 (
Because the layer 2202 can be made relatively thin, it can have a small surface area exposed at the surface of the media facing surface MFS. As a result, diamond embedment during lapping is not as much of a problem as would be the case if the heat sink structure 1912 extended to the media facing surface MFS. Therefore, as long as a relatively non-corrosive material such as those discussed above is used for the layer 2202, it can extend all of the way to the media facing surface MFS, thereby maximizing heat transfer from the near field transducer 1904 to the heat sink structure 1912.
While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the inventions should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
Matsumoto, Takuya, Pentek, Aron, Gorantla, Venkata R K
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